mineralkortikoid

Mineralocorticoids are a class of corticosteroid hormones produced by the zona glomerulosa of the adrenal cortex. The principal mineralocorticoid in humans is aldosterone; deoxycorticosterone (DOC) also has mineralocorticoid activity in some tissues. These hormones regulate electrolyte and fluid balance by promoting sodium reabsorption and potassium excretion in the kidney, primarily in the distal tubules and collecting ducts.

Secretion is stimulated mainly by the renin–angiotensin system: low blood pressure or salt delivery to the kidney increases renin release, leading to angiotensin II–stimulated aldosterone production. Higher plasma potassium also promotes aldosterone release, while the actions of ACTH are mainly transient. Atrial natriuretic peptide inhibits aldosterone secretion. Aldosterone action is modulated by the 11β-hydroxysteroid dehydrogenase type 2 enzyme, which protects mineralocorticoid receptors from cortisol.

Mechanism involves aldosterone binding to intracellular mineralocorticoid receptors (MR) in renal principal cells. The aldosterone–MR complex regulates gene transcription, upregulating epithelial sodium channels (ENaC), Na+/K+ ATPase, and the kinase SGK1. This increases sodium reabsorption and the accompanying water reabsorption, while promoting potassium and hydrogen ion excretion, thus expanding extracellular fluid volume and contributing to blood pressure regulation.

Physiological role includes maintenance of extracellular fluid volume, blood pressure, and acid–base balance, with effects extending to colon and some exocrine tissues. MR are also present in other organs, including the heart, where mineralocorticoids may influence function beyond the kidney.

Clinical aspects include hyperaldosteronism (primary or secondary), which can cause hypertension and hypokalemia; hypoaldosteronism leads to hyponatremia and hyperkalemia. Treatments include MR antagonists (spironolactone, eplerenone) for hyperaldosteronism and fludrocortisone as replacement therapy in Addison’s disease, with careful electrolyte monitoring.